I only realized XMPP support was ending a month ago, I am not sure how I missed the notification but this just introduces a new way for me to miss messages.
I think the writing is on the wall for XMPP, even Cisco is now working on Project Squared/ Spark and I expect will be killing off their Jabber software (The tone from their collaboration SMEs has become quite negative). Personally I believe WebRTC based technology can provide a much better user experience and more powerful capabilities than XMPP. Further, as a front end to SIP, it could be a great thing for interoperability, especially with PSTN. However, it really looks like it is being used as an excuse to create new walled gardens.
Fortunately some carriers are migrating to IMS and provide softclients for computers, tablets and smart phones (Rogers One Number, and Telus Extend). This is the lowest common denominator, but I can chat with everyone with SMS as well as make phone calls from whatever device I choose. However, although technically possible, multiuser chat and presence is still not available.
So here we are 20 years later, and chat is more fragmented than ever, but at least unlimited SMS is now common. AT&T and Verizon are finally beginning migration to IP peering which opens the way for video calling over the PSTN. I think there is an opportunity for carriers here if they would get their act together. 6+ platforms (Skype, Hangouts, FB Messenger, iMessage, BBM, SMS) really doesn't work for me.